Process for structurally thinning materials drilled with via patterns

ABSTRACT

A method for thinning a substrate prior to drilling and/or for structurally reinforcing a thinned substrate having a via pattern after drilling and products resulting thereby. A substrate, or panel, has a first thickness. A pocket is formed in the substrate where the pocket has a second thickness less than the first thickness. At least one via is drilled in the pocket, and the via(s) are filled with an optically transmissive material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.provisional application Nos. 60/810,380, filed Jun. 2, 2006, and60/852,592, filed Oct. 18, 2006, each of which is incorporated herein inits entirety by reference. This application is related to aconcurrently-filed and commonly-assigned U.S. patent applicationentitled “PROCESS FOR OPTICALLY TRANSPARENT VIA FILLING,” Atty. Doc. No.ESI-160-B.

FIELD OF THE DISCLOSURE

The field of the technical subject matter relates to a process forthinning a substrate prior to drilling and/or structurally reinforcing athinned substrate having a via pattern after drilling.

BACKGROUND

Projecting a light through a housing to provide information iscommonplace. Examples include but are not limited to computer keyboardsthat include indication lights for functions such as “Caps Lock” or “NumLock”; computer monitors that include an “on/off” light, automobilesthat include lights to indicate whether heated seats are on or off, orwhether an air bag is on or off; televisions with indicator lights, anda whole host of other consumer electronics.

A common way to provide for such lighting is to provide a projectinglight that is visible when the light is off, and brightly lit toindicate when it is on. A collection of lights, or holes for lights, maybe disruptive to the objectives of an industrial designer.

SUMMARY

Disclosed are methods for improving light transmission and laser drillthroughput by thinning a substrate or panel without substantiallyreducing the strength and durability of the substrate havingthrough-hole vias.

One method of filling a via in a substrate with an opticallytransmissive material taught herein comprises forming a pocket in thesubstrate where the pocket has a second thickness. The second thicknessis less than the first thickness of the substrate. The method in thisexample further includes drilling at least one via in the pocket andfilling the via with an optically transmissive material.

Products formed by the method are also described herein. One example ofsuch a product, a panel by example, has a first thickness and includes asection having a second thickness wherein the second thickness is lessthan the first thickness. The panel further includes a lighttransmissive section formed in that section of the panel having thesecond thickness wherein the light transmissive section is formed by atleast one via filled with an optically transmissive material.

Details of the these aspects, and other inventive features of thedisclosure are discussed below with reference to the drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a schematic representation of a via geometry and themicrographs of the array of vias taken from the back or drill surface inFIG. 1A and from the front or exit surface in FIG. 1B;

FIG. 2 is a schematic representation of an application where the viasare drilled through a substrate having a standard thickness of about 400μm;

FIG. 3 is a schematic representation of an application where the viasare drilled through a substrate having a thinner thickness of about 100μm;

FIG. 4 is a schematic representation of an application where the viasare drilled inside a thinned pocket area of a substrate;

FIG. 5 is a schematic representation of the sequence of method steps ofa substrate having a thinned pocket area reinforced by a solidreinforcing material; and

FIG. 6 is a schematic representation of the sequence of method steps ofa substrate having a thinned pocket area reinforced by a liquidreinforcing material.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

A thinned substrate or panel having through-hole vias (also calledmicro-vias herein due to their relatively small size) made according tomethods taught herein is shown in FIG. 1. The substrate can be thinnedusing standard machining or the substrate can be provided having asection including a reduced thickness. The substrate may incorporate amicro-via pattern array 10 in a substrate surface as shown in FIG. 2.After a micro-via pattern array 10 is drilled in the substrate 12, atransparent or translucent material filler 32 may be applied to thedrilled micro-vias. Then, a material having transparent or translucentand strengthening properties can be applied to the drilled micro-viasubstrate surface to reinforce the strength of the thinned substrate asshown in FIGS. 3 and 4. The reinforcing material 36 could either be asolid that is bonded to the drilled surface or a liquid or viscoussubstance that cures to form a solid. The reinforcing material may alsobe used to color, diffuse, or apply lens effects or other artisticlighting effects in applications where lighted patterns are intended tobe created with the micro-vias.

Referring to FIGS. 3-6 a method for reinforcing a thin substrate 12having via 10 with a light transmissive material and a product made fromusing the method is shown and described below. The method and steps forstructurally reinforcing a thin substrate having via with lighttransmissive material is illustrated in FIGS. 5 and 6. A panel orsubstrate 12 is provided. Substrate 12 is a relatively thin continuoussheet of material such as anodized aluminum. Substrate 12 includes afirst or drill surface 14 and an opposing second or exit surface 18defining a substrate thickness 20. Typically, when the substrate isaluminum, the substrate 12 should be about 400 micrometers (μm) thick inorder for the substrate 12 to retain its structural integrity after thevia array 10 has been drilled in the substrate drill surface 14. In anexample of the present invention, the aluminum substrate 12 provided hasa thin thickness 20 a, that is a thickness of less than 400 micrometers(μm), as shown in FIG. 3. Alternatively, where an aluminum substrate 12having a thickness 20 of about 400 micrometers (μm) is provided, aportion of the substrate 12 can be thinned on the drill surface 14 to athinner thickness 20 a as shown in FIG. 4.

In an application where an aluminum substrate 12 having a thickness of400 micrometers (μm) is provided, the method includes thinning a pocketarea 22 on the drill surface 14 to a thinner thickness 20 a of about 100micrometers (μm). As shown in FIG. 4, the thinned pocket area 22 can bemachined using a bore or other machined device. The size of the thinnedpocket area 22 should be large enough to accommodate the desired viaarray pattern 10. The thinned pocket area 22 is shown in FIG. 4 as ahaving a circular shape, but it is understood that the thinned pocketarea 22 can be of other shapes and configurations. The thinned area 22of the substrate 12 improves light transmission and reduces the laserdrill time of the vias.

In one application of the method shown in FIG. 5, act (referredhereafter as S) 1 includes drilling one or a plurality of micro-vias orholes 24 through the thinned substrate 12. As shown in FIG. 1, in oneaspect, the vias 24 are conical-shaped having sidewalls 26 and a firstopening 28 in substrate drill surface 14 and an opposing second opening30 on substrate exit surface 18. First via opening 28 is larger indiameter than second via opening 30. For example where the substrate 12is aluminum, first via opening 28 is approximately 90-100 micrometers(μm) in diameter and second via opening 30 is approximately 30-40micrometers (μm) in diameter, as shown in FIGS. 1A and 1B. It isunderstood that larger or smaller openings and other via shapes andconfigurations may be used. The vias 24 in FIGS. 1A and 1B are drilledor machined out of the substrate using a laser, such as a diode-pumpedsolid-state pulsed laser 40 in a circular or spiral pattern.

Optionally, cleaning the drilled vias 24 to remove any debris ordeposits formed during the machining process can be performed. It hasbeen shown that a CO₂ snow jet cleaning and isopropyl are effective incleaning the vias. Other via cleaning techniques known by those skilledin the art may also be used. Ultrasonic cleaning using, for example,ultrasonic baths may be used. Also, the application of high-pressureair, like the snow jet, may be made from a source movably located in asimilar manner to the drill 40 to clean the vias.

In S2 shown in FIG. 5, the disclosed method can include applying afiller material coating 32 into the vias 24. The filler material 32 maybe a visible light transmissive material. The exemplary UV curablefiller material 32 is substantially clear when cured. As best seen inFIG. 1, the filter material 32 is applied to the substrate secondsurface 18 over the top of the second or smaller openings 30 of vias 24,filling the vias 24 as shown in FIG. 5. The filler material 32 as shownis applied with a syringe-type device 34. Although the step of fillingthe micro-vias is shown in FIG. 5, the method can proceed to S3 withoutfilling the micro-vias with filler material 32.

Referring to FIG. 5 in S35 a reinforcing material 36 is applied to thethin substrate 12. The reinforcing material 36 having transparent ortranslucent properties is applied to the drilled micro-via substratesurface 14 to reinforce the strength of the thinned substrate 12. Asshown in FIG. 5, the reinforcing material 36 can be a solid preformedand/or pre-cured material having transparent or translucent properties,such as plastic or glass. A solid transparent reinforcing material 36 ofthe appropriate size is applied to the thin substrate as shown in FIG. 3or to the thinned pocket area 22 of a substrate as shown in FIGS. 4 and5. The reinforcing material 36 provides the substrate 12 with thestructural support integrity of a substrate having a normal thickness,for aluminum that of 400 micrometers (μm).

If the vias have been filled in S2 and/or if the reinforcing material 36is not pre-cured, the method may proceed to S4 where preferably a UVclear filler 32 and/or the reinforcing material 36 is then cured byexposing the filler material 32 to UV light through the transparentreinforcing material 36. When cured, the filler material 32 is opticallytransparent permitting passage of visible light through the fillermaterial 32, the reinforcing material 36, and substrate 12 through vias24. The curing of the UV clear filler material 32 bonds the reinforcingmaterial 36 to the substrate 12.

In another example, the method shown in FIG. 6 includes drilling one ora plurality of micro-vias 24 through the thinned substrate 12 in S11. Asshown in FIG. 1, the vias 24 are conical-shaped having sidewalls 26 anda first opening 28 in substrate first surface 14 and an opposing secondopening 30 on substrate second surface 18 as described above. It isunderstood that larger or smaller openings and other via shapes andconfigurations may be used. The drilled vias 24 can be cleaned to removeany debris or deposits formed during the machining process.

The filler material 32 may be a visible light transmissive material. Theexemplary UV curable filler material 32 is substantially clear whencured. Filler material 32 also may have better transmission of audiblesound through the filler material 32 than transmission of audible soundthrough substrate 12 thickness 20. As best seen in FIG. 1, the fillermaterial 32 is applied to the substrate second surface 18 over the topof the second or smaller openings 30 of vias 24, filling the vias 24 asshown in FIG. 5. The filler material 32 as shown is applied with asyringe-type device 34. Although, the step of filling the micro-vias isshown in FIG. 5, the method can proceed to S3 without filling themicro-vias with filler material 32.

In S12 shown in FIG. 6, the disclosed method can include applying aliquid filler material coating 32, such as a clear UV curable epoxy,into the vias 24. As shown in FIG. 6, the filler material 32 is appliedto the substrate second surface 18 over the top of the second or smalleropenings 30 of vias 24 with a syringe-type device 34. Other fillermaterial 32 application devices and techniques known by those skilled inthe art may be used. For example, a thin material film, rather than acurable liquid filler material, can be applied to the drill surface 12of the aluminum substrate 12, resulting in essentially unfilled vias.

If a liquid curable filler material 32 is applied to the micro-vias 24,the method proceeds to S13, where the filler material 32 is then curedby exposing the filler material 32 to UV light. Any excess or uncuredfiller material is removed from the substrate 12. If necessary, themethod may also include additional curing after the excess fillermaterial is removed by, for example, a simple isopropanol wipe.

In S14, a reinforcing material 36 is applied to the thinned pocket area22 of the substrate as shown in FIGS. 4 and 6. The reinforcing material36 can be a liquid or viscous material that cures to form a solidmaterial. A liquid transparent reinforcing material, such a clear epoxyor other reinforcing material provides structural support to the thinnedsubstrate area. The reinforcing material 36 as shown is applied with asyringe-type device 38. Other application devices and techniques knownby those skilled in the art may be used. The reinforcing material 36,when cured provides the substrate with a uniform structural integritylike that of a substrate having a conventional thickness.

The use of vias 24 and an optically transparent reinforcing material 36and/or filler material 32 produces a smooth and continuous substratesurface to the naked eye that is capable of displaying controlled imagesthrough the vias from interior illumination. The resultant substrate 12can be used in all manner of application. The disclosed method andresultant substrate is applicable in virtually all applications where avisually continuous and uninterrupted substrate surface is desiredhaving the capability to produce illuminated messages, images or otherperceptible characteristics for the user.

For example, the substrate 12 of FIGS. 3 and 4 is in the form of apanel. The panel 12 can be incorporated in a conventional housing aspreviously discussed or can be integral with a housing. When the panel12, as part of a housing, is back lit with an LED, fluorescent orincandescent light, or other lighting device, the light emitted from thevias forms a pattern visible to the viewer.

In another example, the substrate can be thinned in a small area withoutapplication of a reinforcing material to the thinned area. In thisexample, thinning the small area of the substrate should not reduce thestructural strength of the substrate, obviating the need for areinforcing material. The size of the thinned area possible in thesubstrate in order maintain the structural integrity of the substrate asa whole is dependent on the density of the drilled micro-via array, thestrength of the substrate material, and/or the shape of the drilledvias, etc.

While the method has been described in connection with what is presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the method is not to be limited to the disclosedembodiments but, on the contrary, is intended to cover variousmodifications and equivalent steps and arrangements included within thespirit and scope of the invention and any appended claims.

1. A method of filling a via in a substrate with an opticallytransmissive material, the substrate including a first thickness; themethod comprising: forming a pocket in the substrate, the pocket havinga second thickness, the second thickness being less than the firstthickness; drilling at least one via in the pocket; and filling the viawith an optically transmissive material.
 2. The method as in claim 1wherein the optically transmissive material is curable; and the methodfurther comprising: curing the optically transmissive material afterfilling the via.
 3. The method as in claim 2, further comprising:filling the pocket with an optically transmissive material.
 4. Themethod as in claim 3 wherein the optically transmissive material issolid.
 5. The method as in claim 3 wherein the first thickness is equalor greater than 400 micrometers and the second thickness is equal to orless than 100 micrometers.
 6. The method as in claim 1 wherein the viais conically shaped.
 7. The method as in claim 6 wherein the viaincludes a first end having a first diameter between 90 to 100micrometers and a second end having a second diameter between 30 to 40micrometers.
 8. The method as in claim 1 wherein the via is drilled by alaser.
 9. A panel having a first thickness, the panel including asection having a second thickness wherein the second thickness is lessthan the first thickness, the panel including light transmissive sectionformed in that section of the panel having the second thickness, thelight transmissive section being formed by at least one via filled withan optically transmissive material.
 10. The panel as in claim 9 whereinthe section having the second thickness forms a pocket, the pocket beingfilled by an optically transmissive material.
 11. The panel as in claim10 wherein the optically transmissive material filling the pocket is aUV curable polymer.
 12. The panel as in claim 10 wherein the pocket hasa thickness of equal to or less than 100 micrometers.
 13. The panel asin claim 11 wherein the via is conical.
 14. The panel as in claim 13wherein the via includes a first diameter between 90 and 100 micrometersand a second diameter between 30 and 40 micrometers.
 15. The panel as inclaim 14 wherein the light transmissive section includes multiple viasorganized into a pattern.